Detectors of oil mists and the like



May 10, 1960 A. MATHISEN 2,935,909

DETECTORS OF OIL MISTS AND THE LIKE Filed April 11, 1958 2 Sheets-Sheet1 ANbEks Mm'wssu A'r'roRNEYy,

May 10, 1960 A. MATHISEN 2,935,909

DETECTORS OF OIL MISTS AND THE LIKE Filed April 11, 1958 2 Sheets-Sheet2 INVENTOR ANbERs mmmssn ATTORNEY! DETECTORS OF OIL MISTS AND THE LIKEAnders Mathisen, Alvel'stoke, England, assignor t Graviner ManufacturingCompany Limited, London, England, a British company This inventionrelates to detectors of oil mist and the like.

In the specification of U.S. application Serial No.

629,920, filed December 21, 1956, now US. Patent No.-

2,907,993, we have described a detector of this kind in which gas, whichmay be carrying such mist, is drawn through a space across which a lightbeam is projected. Transparent windows are provided on opposite sides ofthis space and an electric lamp is mounted behind one window and aphoto-electric cell behind the other window, the passage of mist throughthe space serving to reduce the amount of light from said lamp whichfalls on the photo-electric cell. 'The consequent change in output ofthe photo-electric cell is used to operate appropriate indicating oralarm apparatus.

It has been found that under certain conditions, when using a detectorhaving the construction described in the aforesaid specification,abnormal deposits may occur on the transparent Windows. These depositsmay not only be of oil or other vapour but may also consist of particlesof combustion products such as soot or carbon dust. Whilst such depositsdo not in any Way prevent correct operation of the detector,nevertheless they render clean- I ing of the windows necessary at morefrequent intervals fan, this vortex causing the soot or other dust to beprojected outwards from the vortex and deposited upon the windows.

In an endeavour to avoid such troubles, the present invention provides adetector of oil mist and the like comprising a chamber having an inletfor gas which may carry such mist, a window in one wall of said chamber,a second window in another wall of said chamber, a duct extending from aposition adjacent but spaced from said first Window to a positionadjacent but spaced from said second window, a cuff surrounding saidfirst window, said cuff extending through an opening in said duct withthe periphery of said cuff spaced from said opening, a second cuffsurrounding said second window and extending tates atent 2,935,909Patented May 10, 1960 first cuff, said duct having a second openingtherein into which said second cuff extends, the area of said secondopening being greater than the cross-sectional area of said second cuff,an outlet for gas located in said duct at a position between the twoopenings, and means for mounting a light source behind one window forprojecting light through said duct onto a photo-electric cell mountedbehind the other window, the arrangement being such that gas passingfrom said inlet to said outlet passes through the spaces between thecuffs and the respective openings in said duct.

Two constructions of oil mist detectors in accordance with the presentinvention will now be described, by way of example only, reference beingmade to the accompanying drawings in which:

Figure l is a side view, partly in section, of the first construction ofoil mist detector,

Figure 2 is an end view, partly in section of the detector shown inFigure 1, and

Figure 3 is a side View of the second construction of oil mist detector.

Referring firstly to Figures 1 and 2, it will be seen that thisconstruction of detector is generally similar to that shown in Figures 1to 3 of the drawings accompanying the aforesaid patent specification. Aswith the previous construction, there is a monitoring chamber 10 throughwhich gas, which may be carrying oil mist, is drawn by means of asuction fan 11 through a suction pipe 12 the inlet 12a of which isconnected to the source which is to be monitored. Windows 13 and 14 areprovided on opposite sides of the monitoring chamber 10 and an electriclamp 15 is mounted behind thewindow 14 to project light across thechamber 10 through the window 13 onto a photo-electric cell 16 of thevacuum tube type which is mounted behind the window 13. To compensatefor temperature and voltage changes, the output of the cell I into themonitoring chamber 10. In the interior of the through an opening in saidduct with the periphery of said cuff spaced from said opening, and anoutlet for gas from a position in said duct intermediate its twoopenings, the arrangement being such that gas entering said inletpassesaround the outside of either cuff and thence into said duct and outthrough said outlet.

The invention further provides a detector of oil mist chamber 10 arectangular cross-section duct 23 is fitted which overlaps the end ofeach of the culfs 21, 22 but does not extend to the walls of themonitoring chamber 10. Within the duct 23 and overlapping the upper sideof each of the cuffs 21, 22 an arcuate vortex shield 24 is provided,this shield 24 being secured along its centre line to each of the cuffs21, 22 and having a larger radius of curvature than the radius of thecufis 21, 22. An outlet tube 25 extends from an opening in the top ofthe duct 23 to the inlet of the fan 11.

To give access to the windows 13, 14, a door 23a is provided in' theside of the duct 23 and, if desired, a window (not shown) can also beprovided in the side of the duct 23 to allow observation through acorresponding window 26a provided in a removable closure plate 26 whichis removed to give access to the door 23a.

In, operation the gases or vapours from the inlet elbow pipe 12 passinto the duct 23 through its open ends around the sides of the cuffs 21,22 and this results in a horizontal gas or vapour column in front of thewindows 13, l l'which can result in an improved sensitivity toobscuration of the light column. The gases and vapours leave the duct 23by passing around the edges of the vortex shield 24 and into the outlettube 25 leading to the fan 11. It is found that where there waspreviously astendencyto form a .vortexwithin. the. monitoring chamber10, any vortex will now be formed in the tube 25 above the vortex shield24. It has also been found that with such anarrangement thetendency;forsolids to. be deposited; on the; windows;l3 and ,i tcis,substantially reduced, suchdepositsaoccurringeitherbefore the gasesOI'WVBPOUI'S'CillIfiI the duct 23 -101 after ,theyhave. passed into thetube 25.

-=Ref,erring-now to Figure:3, :thesecond construction of oilmistdetector is arranged to draw: gas-from the -space-tobemonitored, forexample, the crankcase of an engine, via Zthe inlet at by .having 3the-outlet 31.0011- nected to a suction source; ;in the case ofanqen'ginethe latter may be the induction systemg in. which, case no J opens intoaycylindrical, monitoring chamber 32 in which a cylindrical i duct 133,,-of;.-,sm all er diameter than the chamber 32 and of shorter length, isrnounted coaxnially relative to the chamber 32. ,;At eachend of themonitoring chamber 32, windows 34 and 35 are provided,

,andras with thefirst construction a lamp 35 is mounted electric cell 33is mounted behind the window 35.

in a housing 37 behind the window 34 and a-photo- In this particularconstruction the cell 38 is a'barrier layer cell,

duct-33 ata position midway alongits length. Thus,

-as'.with the first described construction, gas is drawn ,in through theinlet 30 and passes towards each end of the chamber 32 through theannular space between the ,chamben32 and the duct 33, thence around theends 33a and- 33b respectively and through the annular spaces betweenthe cuff-39 and mouth 33a on'the onehand, and thecuif 40 and themouth-33b on theother hand, and

back towardslthe middle of'the duct 33 and out through the outlet31. Inthis way, it is ensured that the flow ofmiSt-laden gas is always awayfrom the Windows 34,

and 3S and danger of deposit of oil and-dirt on these ,windows isconsiderably reduced. As with the first described construction, theoutput of the cell 35 may normally be balanced bythe output, from asimilar cell which is located so that, its illumination isnot, affectedby the presence. of oil mist.

.I-claim: 1. .In; a detector ofoilumist andthe, like,- a chamber having.an;inlet for gas which may carry such mist, azwindow in one wall ofsaid chamber, asecond window in another. wall or" said chamber, a ductextending from a position adjacentvbut spacedfrom said firstwindow to aposition adjacent but spaced from said second window, a:first vcuifsurrounding said first window, said duct having an -=opening thereininto which saidcuff extends with the periphery of said cuff spaced fromsaid opening, a second cuff surrounding said second window, said-ducthaving a furtheropening therein into which rsaidsecond cuff extends withthe periphery ofsaid second .cuft' spaced-from said further opening,said duct having an outlet for gas located at a position in said ductinter- ..mediate its two .openings, a suctionfan, said suction fanhaving a suction inlet, said suction inlet being connected to said ductoutlet whereby gas entering the gas inlet of said chamber is drawnaround the outside of either 5 cult and thence into said duct and outthrough said gas outlet, and a deflector plate, said deflector platebeing mounted in said'duct directly below the gas outlet and havingagreater surface area than the area of said gas outlet, whereby anyvortex produced by said suction fan is located on the side of the.deflector plate facing into said gas outlet.

2. A detector according to claim 1, wherein said deflector plate partlyoverlaps both said first cuff and said second cuif.

3. A detector accordingto claim 1, wherein said plate is of arcuatecross-section with its convex surface facing away from the gas outlet insaid duct.

4. A detector of oil mist and the like comprisinga chamber having aplurality of walls, one of said walls having therein an inlet for gaswhich maycarry such rnist, a first'window, said window being mounted inone ofsaid Walls, a'second window, said second window being mounted' ina different one of said walls from that in which said first window ismounted, a first cuff surroundmg said first window and projecting intosaid chamber,

-a second cuff surrounding said second window and 'pro- -jecting intosaid chamber, a duct mounted in said chamber, said duct having anopening therein into which -said first cuifextends, the area of saidopening being -greater thanthe cross-sectional area of said-first cuff,=saidduct-ha'ving a second-opening therein into which said second cuifextends, the area of said second opening being greater than thecross-sectional area of said second cuff,

Ysaid'duct having an outlet for gas located in the upper 35. surface ofsaid, duct at a position between the two openings, means fonmountingaphoto-electric cell behind one window, means'for'mounting a lightsource behind the .other'window for projecting light through said ductonto said photoelectric cell, a suction fan, said suction fan 40 havinga suction inlet, said suction inlet being connected to said ductoutlet,. and a vortex deflector plate, said vortex deflector. platebeing mounted in said duct adjacent. but spaced from the upper surfacethereof, said deflectorplate extending across the full extent of saidduct. outletwhereby any vortex producedby said suction :fanis located onthe side ofthe" deflector plate facing into said gas outlet.

' 5."A. detectoraccording-tor claim 4, wherein said ,deflectorplatepartly overlaps both said first cod and said secondcutf.

6. -A'; detector according to claim 4, wherein said plate risofiarcuate' cross-section with its convex surface facing away from-the gasoutlet in said duct.

-Rei er ences,Cited;in the file of this patent V UNITED STATES PATENTS2,042,095 Grant May 26, 1936 2,770,162 Fleming Nov. 13, 1956 so "FOREIGNPATENTS 726,484 France, Mar. 7, 1932 704,052 Great Britain Feb. 17, 1954

